The invention is in the field of high-voltage lateral semiconductor devices, and relates more particularly to lateral silicon carbide (SiC) semiconductor devices suitable for high-voltage applications.
In various applications, such as traction control systems in locomotives and the electrical systems in electric vehicles, semiconductor devices which can support high voltages, typically up to 5,000 Volts, are desirable. Additionally, such devices should be able to operate at high temperatures and at relatively high frequencies, typically above 150 kHz. Although certain silicon devices, such as thyristors, which can support 5,000 Volts presently exist, these devices are not able to operate at high temperatures and frequencies due to the inherent limitations of silicon as a semiconductor material.
In order to overcome the drawbacks of silicon, it has been proposed to use silicon carbide in fabricating high-voltage, high-frequency, high-temperature semiconductor devices. Under such operating conditions, unipolar devices are superior to bipolar devices, and lateral unipolar devices are superior to vertical unipolar devices because lateral devices can provide a smaller "on" resistance and therefore lower losses than comparable vertical devices.
The use of silicon carbide in a high-voltage lateral unipolar device is shown in "High voltage (450 v) 6H-SiC lateral MESFET structure", D. Alok et al, Electronics Letters, Vol. 32, No. 20, pp. 1929-1931, 1996. This reference describes a lateral MESFET SiC structure capable of withstanding a forward blocking voltage of 450 Volts, a level which is about 2-3 times higher than previously reported for lateral SiC MESFET devices.
While this earlier work of a present co-inventor represents a substantial advance in the art, it would nevertheless be desirable to have a lateral unipolar device capable of operating at substantially higher voltages while providing good high-temperature and high-frequency performance in a relatively compact structure.